0211100930 - Mfm Ii - Smooth Muscle (Fitzovich)

Front 1

What intracellularly increasing ion causes smooth and skeletal muscle contraction?

Back 1

Ca++ that moves across the sarcolemma. Ca crosses the cell membrane, NONE comes from the sarcoplasmic reticulum.

Front 2

What unique kind of contraction occurs with smooth muscle?

Back 2

tonic contraction causing the shape to change and stay that way for a long time

Front 3

What two general system control smooth muscle?

Back 3

neural
hormonal

Front 4

How is smooth muscle classified?

Back 4

phasic vs. tonic

OR

single unit vs. multi unit

Front 5

What is the difference between phasic and tonic?

Back 5

1. phasic - phasic contractions via action potentials like foodway peristalsis smooth muscle
2. tonic - sustained contractions not associated with action potentials like phasic. these are like sphincters, blood vessels, airways

Front 6

What is the difference between single unit and multi-unit smooth muscle classification?

Back 6

single-unit - the entire muscle body acts a single unit because it is electrically coupled

multi-unit - muscle body is NOT electrically coupled so difference cells act independently

Front 7

What is the difference between extrinsic innervation and intrinsic innervation?

Back 7

extrinsic is from the ANS
intrinsic is inherent in the target system like GI

Front 8

What is adenosine?

Back 8

released by active skeletal muscle during exercise and relaxes smooth muscle to allow more blood to get to skeletal muscle

Front 9

How does phosphorylation of myosin light chains effect force in smooth muscle?

Back 9

more phosphorylation -> greater force, greater velocity

Front 10

What is unique about smooth muscle to change the force-velocity relationship and how is it accomplished?

Back 10

the number of active crossbridges and their cycling rate can be adjusted by adjusting two things:
1. intracellular calcium level
2. phosphorylation of myosin

Front 11

What are the detailed steps of crossbridge regulation in smooth muscle?

Back 11

1. intracellular Ca++ increases
2. 4 Ca++ binds calmodulin
3. Ca-calmodulin binds to myosin light chain kinase and activates it
4. MLCK uses ATP to phosphorylate a regulatory site on myosin, which makes it capable of binding actin
5. Also, for myosin to bind, it must be available per ATP attachment in the past, which energizes it and detaches it from a previously attached actin filament
6. Now the myosin is available and capable so it attaches to actin and cycles
7. crossbridge swings, the "now ADP" and Pi attached to the myosin head dissociate from the head
8. ATP binds to myosin head to break the actin bond to prepare for the next cycle

Front 12

Does the myosin light chain need to be phosphorylated for every cycle?

Back 12

nope, but if it is ever dephosphorylated, then it needs to be phosphorylated (capable) for it to happen again

Front 13

What is myosin phosphatase?

Back 13

MP attaches to the myosin head in the absence of MLCK to stop the myosin light chain from being capable.

smooth muscle contraction regulation then is a balance between MP and MLCK

Front 14

What are the two ways that Ca++ is regulated in muscle?

Back 14

1. release from SR by second messengers
2. influx across the sarcolemma

Front 15

What types of channels allow Ca++ to move across the sarcolemma?

Back 15

receptor-activated
potential-dependent

Front 16

What is the cascade to release Ca++ in muscle?

Back 16

receptor-activated
1. agonist binds receptor
2. receptor sends signal through G protein
3. G protein turns on PLC and Rho-kinase
4. PLC produces IP3; Rho-kinase inhibits MP
5. IP3 opens Ca++ channels on SR
6. Ca++ binds to myosin light chain kinase
7. contraction

Front 17

How does cAMP work on smooth muscle?

Back 17

cAMP phosphorylates MLCK and reduces it's activity just like a reduction of intracellular Ca++

Front 18

What does norepi and epi do to smooth muscle and how?

Back 18

contraction if binding to alpha-andrenergic receptor and increasing IP3

relaxation if binding to beta-adrenergic receptors and increasing cAMP levels

Front 19

What does acetylcholine do to smooth muscle and how?

Back 19

contraction if attaches to smooth muscle M3 receptors and increases IP3

relaxation if attaches to endothelial M3 receptor and increases NO

Front 20

What does Angiotensin II do to smooth muscle and how?

Back 20

contraction by attaching to AT-II receptor and increasing IP3

Front 21

What does ADH/vasopressin do to smooth muscle and how?

Back 21

contraction by attaching to AVPR1A (V1) receptor and increasing IP3

Front 22

What does endothelin do to smooth muscle and how?

Back 22

contraction by attaching to endothelin receptor and increasing IP3

known as most powerful vasoconstrictor

Front 23

What does adenosine do to smooth muscle and how?

Back 23

relaxation by binding to adenosine receptor and increasing cAMP levels

Front 24

How is Ca++ moved out of the cell?

Back 24

Na/Ca exchanger by using the Na concentration gradient and then using the Na/K ATPase pump to push Na back out of the cell. if the Na/K pump is broken, then Ca will build up and force will increase!

Front 25

Where is Ca moved from/to?

Back 25

inside cell <-> outside cell
inside SR <-> outside SR